A massive 1.4 tonne-World War II bomb will explode in a controlled environment in Frankfurt, Germany on Sunday.

According to sources, patients at hospitals in the city have been moved in preparation for a safe explosion of the bomb which was found in a building site on Wednesday.

The evacuees include premature babies and people in intensive care.

The police have warned that about 65,000 people must leave their homes, insisting that anyone who refuses to move will be put in prison.

According to the police, an uncontrolled explosion of the HC 4000 bomb would be powerful enough to flatten an entire street. The operation will take at least 12 hours and evacuees will have to leave their homes by 06:00 GMT.

This is apparently Germany’s biggest post-war evacuation. A smaller one took place recently in Koblenz.

About 2,000 tonnes of unexploded bombs, on average, are found each year in Germany. It’s estimated that about half of the 2.7 million tonnes of bombs dropped by allied forces during World War II landed on German soil (compared to about 74,000 tonnes of bombs dropped on the UK by Germany).

Many of the bombs were equipped with malfunctioning time-delay fuses, and many never went off. There were also Russian artillery shells, German hand grenades and tank mines as well as Russian munitions from training facilities in post-war East Germany.

In August this year, a kindergarten was evacuated after a teacher found an unexploded World War II bomb on a shelf. Police said a child had found it on a woodland walk and brought it inside.